CH01::History: clarify Nakamoto & PoW facts

- Bitcoin was invented in 2007 (not 2008) per Nakamoto saying he'd
  worked on it for about a year and a half prior to publication.  Update
  text to just say "first described in 2008"

- Of the inventions Bitcoin combined, b-money wasn't one of them.  We
  know that Nakamoto sent his original paper to Adam Back, Back told
  Nakamoto about Wei Dai's b-mony, and Nakamoto contacted Dai in order
  to add the b-money reference to his paper as an example of a previous
  related idea.  Nakamoto was aparently unaware of b-money before then
  and so couldn't have combined it with other ideas in the creation of
  bitcoin.  Updated text from "b-money" to say "digital signatures",
  which is a critical technology that was obviously part of Bitcoin's
  original combination.

- The text describes "the" critical invention of Bitcoin as using PoW to
  conduct an global election.  Although that was critical, other factors
  may also have been critical (e.g. difficulty adjustments to keep the
  rate of issuance relatively constant).  Updated text to say "a"
  critical invention.

- Changed Bitcoin from exceeding the combined processing power of top
  super computers to exceeding the number of computing operations.
  It's not really fair to compare ASICs to general purpose CPU chips;
  it's like comparing a wrench to your hand.

- Updated the dollar value of the largest transaction to "over a billion
  dollars"; dropped the amount of the transaction fee.  I think this
  will better future-proof the text.

ch01.asciidoc

@@ -93,17 +93,17 @@ When cryptography started becoming more broadly available and understood in the
 === History of Bitcoin
 
 ((("Nakamoto, Satoshi")))((("distributed computing")))((("bitcoin",
-"history of")))Bitcoin was invented in 2008 with the publication of a
+"history of")))Bitcoin was first described in 2008 with the publication of a
 paper titled "Bitcoin: A Peer-to-Peer Electronic Cash
 System,"footnote:["Bitcoin: A Peer-to-Peer Electronic Cash System,"
 Satoshi Nakamoto (https://bitcoin.org/bitcoin.pdf).] written under the
 alias of Satoshi Nakamoto (see <<satoshi_whitepaper>>). Nakamoto
-combined several prior inventions such as b-money and HashCash to create
+combined several prior inventions such as digital signatures and Hashcash to create
 a completely decentralized electronic cash system that does not rely on
 a central authority for currency issuance or settlement and validation
 of transactions. ((("Proof-of-Work algorithm")))((("decentralized
 systems", "consensus in")))((("mining and consensus", "Proof-of-Work
-algorithm")))The key innovation was to use a distributed computation
+algorithm")))A key innovation was to use a distributed computation
 system (called a "Proof-of-Work" algorithm) to conduct a global
 "election" every 10 minutes, allowing the decentralized network to
 arrive at _consensus_ about the state of transactions. ((("double-spend
@@ -117,12 +117,11 @@ The Bitcoin network started in 2009, based on a reference implementation
 published by Nakamoto and since revised by many other programmers. The
 implementation of the Proof-of-Work algorithm (mining) that provides
 security and resilience for Bitcoin has increased in power
-exponentially, and now exceeds the combined processing power of the
+exponentially, and now exceeds the combined number of computing operations of the
 world's top supercomputers. Bitcoin's total market value has at times
 exceeded $1 trillion US dollars, depending on the bitcoin-to-dollar
 exchange rate. The largest transaction processed so far by the network
-was $400 million US dollars, transmitted instantly and processed for a
-fee of only $1.
+was over a billion US dollars.
 
 Satoshi Nakamoto withdrew from the public in April 2011, leaving the responsibility of developing the code and network to a thriving group of volunteers. The identity of the person or people behind Bitcoin is still unknown. ((("open source licenses")))However, neither Satoshi Nakamoto nor anyone else exerts individual control over the Bitcoin system, which operates based on fully transparent mathematical principles, open source code, and consensus among participants. The invention itself is groundbreaking and has already spawned new science in the fields of distributed computing, economics, and econometrics.